• Transactions on Electrical and Electronic Materials
• /
• v.18 no.4
• /
• pp.181-184
• /
• 2017

Multilayer ceramics in which piezoelectric layers of $0.90Pb(Zr_{0.48}Ti_{0.52})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3-0.05Pb(Zn_{1/3}Nb_{2/3})O_3$ (0.90PZT-0.05PMS-0.05PZN) stack alternately with silver electrode layers were prepared by an advanced low-temperature co-fired ceramic (LTCC) method. The electrical properties and bonding strength of the multilayers were associated with the interface morphologies between the piezoelectric and silver-electrode layers. Usually, the inner silver electrodes are fabricated by sintering silver paste in multi-layer stacks. To improve the interface bonding strength, piezoelectric powders of 0.90PZT-0.05PMS-0.05PZN with an average particle size of $23{\mu}m$ were added to silver paste to form a gradient interface. SEM observation indicated clear interfaces in multilayer ceramics without powder addition. With the increase of piezoelectric powder addition in the silver paste, gradient interfaces were successfully obtained. The multilayer ceramics with gradient interfaces present greater bonding strength as well as excellent piezoelectric properties for 30~40 wt% of added powder. On the other hand, over addition greatly increased the resistance of the inner silver electrodes, leading to a piezoelectric behavior like that of bulk ceramics in multilayers.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.27 no.2
• /
• pp.55-62
• /
• 2021

This study aims to reduce the rancid odor generated during the fermentation process of kimchi by inserting zinc oxide (ZnO) into an inorganic porous material with a high surface area to decompose or adsorb the fermentation odor. ZnO activated by the presence of moisture exhibits decomposition of rancid odors. Mixed with Titanium dioxide (TiO₂), a photocatalyst. To manufacture the packaging liner used in this study, NaOH, ZnCl₂, and TiO₂ powder were placed in a tank with diatomite and water. The sludge obtained via a hydrothermal ultrasonication synthesis was sintered in an oven. After being pin-milled and melt-blended, the powders were mixed with linear low-density polyethylene (L-LDPE) to make a masterbatch (M/B), which was further used to manufacture liners. A gas detector (GasTiger 2000) was used to investigate the total amount of sulfur compounds during fermentation and determine the reduction rate of the odor-causing compounds. The packaging liner cross-section and surface were investigated using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to observe the adsorption of sulfur compounds. A variety of sulfur compounds associated with the perceived unpleasant odor of kimchi were analyzed using gas chromatography-mass spectrometry (GC-MS). For the analyses, kimchi was homogenized at room temperature and divided into several sample dishes. The performance of the liner was evaluated by comparing the total area of the GC-MS signals of major off-flavor sulfur compounds during the five days of fermentation at 20℃. As a result, Nano-grade inorganic compound liners reduced the sulfur content by 67 % on average, compared to ordinary polyethylene (PE) foam liners. Afterwards SEM-EDS was used to analyze the sulfur content adsorbed by the liners. The findings of this study strongly suggest that decomposition and adsorption of the odor-generating compounds occur more effectively in the newly-developed inorganic nanocomposite liners.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.846-850
• /
• 2002

A PMN-PT-BT/Ag composite was prepared by surface modification with MgO sol with hoping to suppress silver's migration during sintering. The mixture of PbO, $N_2O_5,\;TiO_2\;with\;Mg(NO_3)_2$ instead of MgO was ball milled, the solvent was removed and then the dried powders were calcined at 950$^{\circ}C$/1h. The calcined powder were treated with 3.0 mol% $Ag_2O$ and 1.0 wt% MgO sol and calcined at 550$^{\circ}C$/1h. The dielectrics sintered at 1000$^{\circ}C$/4h under a flowing oxygen showed the density of 7.84g/$cm^3$, the room temperature dielectric constant of 18400, the dielectric loss of 2.4%, the specific resistivity of $0.24{\times}10^{12}{\Omega}{\cdot}cm$. It also showed the bending strength of $120.7{\pm}11.26$ MPa and the fracture toughness of $0.87{\pm}0.002\;MPam^{1/2}$ which were comparable to commercial PZT. The microstructure sonsisted of grains of ∼4${\mu}m$. SEM and SIMS analysis showed that Ag grew as ∼1${\mu}m$ and excess MgO as ∼0.5${\mu}m$.

• Journal of Sensor Science and Technology
• /
• v.22 no.2
• /
• pp.130-135
• /
• 2013

This study proposed a noble process to fabricate TSV (Through Silicon Via) structure which has lower cost, shorter production time, and more simple fabrication process than plating method. In order to produce the via holes, the Si wafer was etched by a DRIE (Deep Reactive Ion Etching) process. The via hole was $100{\mu}m$ in diameter and $400{\mu}m$ in depth. A dielectric layer of $SiO_2$ was formed by thermal oxidation on the front side wafer and via hole side wall. An adhesion layer of Ti and a seed layer of Au were deposited. Soldering process was applied to fill the via holes with solder paste and metal powder. When the solder paste was used as via hole metal line, sintering state and electrical properties were excellent. However, electrical connection was poor due to occurrence of many voids. In the case of metal powder, voids were reduced but sintering state and electrical properties were bad. We tried the via hole filling process by using mixing solder paste and metal powder. As a consequence, it was confirmed that mixing rate of solder paste (4) : metal powder (3) was excellent electrical characteristics.

• Journal of Powder Materials
• /
• v.29 no.6
• /
• pp.468-476
• /
• 2022

Yttria-stabilized zirconia (YSZ) has a low thermal conductivity, high thermal expansion coefficient, and excellent mechanical properties; thus, it is used as a thermal barrier coating material for gas turbines. However, during long-time exposure of YSZ to temperatures of 1200℃ or higher, a phase transformation accompanied by a volume change occurs, causing the YSZ coating layer to peel off. To solve this problem, YSZ has been doped with trivalent and tetravalent oxides to obtain coating materials with low thermal conductivity and suppressed phase transformation of zirconia. In this study, YSZ is doped with trivalent oxides, Nd₂O₃, Yb₂O₃, Al₂O₃, and tetravalent oxide, TiO₂, and the thermal conductivity of the obtained materials is analyzed according to the composition; furthermore, the relative density change, microstructure change, and m-phase formation behavior are analyzed during long-time heat treatment at high temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1992.11a
• /
• pp.38-41
• /
• 1992

Pb(Zr,Ti)$O_3$ powders were synthesized by the partial oxalate method and the modified partial oxalate method, where the difference between the two is the use of pre-reacted (Zr,Ti)$O_2$ in the former method. When compared with conventional mixed oxide method, calcination temperature can be reduced to less than $700^{\circ}C$ by both partial oxalate methods, and the resulting particle size was finer and more uniform. Using partial oxalate-derived PZT powders, sintering temperatures can also be reduced as low as $950^{\circ}C$ without sacrificing desired dielectric and piezoelectric properties, such as relative permittivity, electromechanical coupling factor, and piezoelectric coefficient. Two partial oxalate methods yield ceramics with almost the same physical and electrical properties, so that the step of producing ZTO powder does not seem to be necessary.

• Journal of Powder Materials
• /
• v.26 no.6
• /
• pp.487-492
• /
• 2019

Titanium dioxide (TiO₂) is a typical inorganic material that has an excellent photocatalytic property and a high refractive index. It is used in water/air purifiers, solar cells, white pigments, refractory materials, semiconductors, etc.; its demand is continuously increasing. In this study, anatase and rutile phase titanium dioxide is prepared using hydroxyl and carboxyl; the titanium complex and its mechanism are investigated. As a result of analyzing the phase transition characteristics by a heat treatment temperature using a titanium complex having a hydroxyl group and a carboxyl group, it is confirmed that the material properties were different from each other and that the anatase and rutile phase contents can be controlled. The titanium complexes prepared in this study show different characteristics from the titania-formation temperatures of the known anatase and rutile phases. It is inferred that this is due to the change of electrostatic adsorption behavior due to the complexing function of the oxygen sharing point, which crystals of the TiO₆ structure share.

• Journal of Electrochemical Science and Technology
• /
• v.15 no.3
• /
• pp.345-352
• /
• 2024

The synthesis of Pt nanoparticles and catalytically active materials using the electrochemical top-down approach involves dispersing Pt electrodes in an electrolyte solution containing alkali metal cations and support material powder using an alternating pulsed current. Platinum is dispersed to form particles with a predominant crystallographic orientation of Pt(100) and a particle size of approximately 7.6±1.0 nm. The dispersed platinum particles have an insignificant content of PtO_x phase (0.25±0.03 wt.%). The average formation rate was 9.7±0.5 mg cm^-2 h^-1. The nature of the support (carbon material, metal oxide, carbon-metal oxide hybrid) had almost no effect on the formation rate of the Pt nanoparticles as well as their crystallographic properties. Depending on the nature of the support material, Pt-containing catalytic materials obtained by the electrochemical top-down approach showed good functional performance in fuel cell technologies (Pt/C), catalytic oxidation of CO (Pt/Al₂O₃) and electrochemical oxidation of methanol (Pt/TiO₂-C) and ethanol (Pt/SnO₂-C).

• Journal of Surface Science and Engineering
• /
• v.39 no.4
• /
• pp.190-197
• /
• 2006

The effects of blasting and acidic treatment on the corrosion characteristics of dental implant fabricated with Cp-Ti and Ti-6Al-4V alloy have been researched by using electrochemical methods. The fabricated implants were cleaned and sandblasted by $Al_2O_3$ powder and then acidic treatment was carried out in nitric acid solution. The surface morphology were observed using scanning electron microscope. The corrosion behaviors were investigated using potentiosat and EIS in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The potentio-dynamic test in 0.9% NaCl indicated that the corrosion potential of blasting and acidic treated implant was lower than that of non treated implant, but current density was higher than that of non treated implant. From the cyclic potentiodynamic test results of Ti implant, the passivation current density of blasting and acidic treated implant slightly higher than that of non treated implant. From A.C. impedance test results in 0.9% NaCl solution, polarization resistance($R_p$) value of blasting and acidic treated implant was lower than that of non treated implant. In case of blasting and acidic treated implant surface, the pits were observed in valley and crest of implant surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.325-325
• /
• 2008

스크린 프린팅에 의한 압전 후막은 MEMS 공정을 이용하여 마이크로 펌프, 마이크로 벨브, 마이크로 센서, 마이크로 로봇 등 여러 초소형 기계부품에 응용되고 있으며, Sol-Gel, PLD를 이용해 증착된 막 등에 비해 수십${\mu}m$의 비교적 두꺼운 막을 형성시킬 수 있는 장점을 가지고 있다. 그러나 실리콘 기판을 사용하여 스크린 프린팅으로 형성된 압전 후막의 경우, 공정상 바인더를 연소시키는 과정을 거치게 되므로, 밀집된(Dense) 구조를 가지는 막을 만들기가 어렵다. 이로 인해 스크린 프린팅에 의한 후막은 전기적 특성 및 기계적 특성이 떨어지는 경향이 있다. 본 연구에서는 스크린 프린팅에 의한 압전 후막의 밀집된 구조 및 특성을 향상시키기 위해 0.01Pb$(Mg_{1/2}W_{1/2})$O3-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3-0.35PbTiO_3-0.23PbZrO_3$의 powder와 Attrition 밀링 처리된 powder를 비율별로 혼합하여 입자의 크기를 변화시켜 막의 충진 밀도를 향상시켰으며, 열처리 효과를 극대화시키기 위해 RTA(Rapidly Thermal Annealing)를 통해 열처리 하였다. Attrition 밀링에 의한 파우더를 각각 비율별로 100%, 50%, 25%로 혼합하여 만든 압전 세라믹 페이스트는 P-type(100)Si Wafer sample 위에 $1{\mu}m$의 하부전극용($1100^{\circ}C$) Ag 전극을 screen print하여 소결했다. 그리고 다시 전극이 형성된 Si wafer 위에 스크린 프린팅하고, 건조 한 후 RTA로 300초 동안 열처리 한 결과 밀집된 구조를 가지는 압전 후막을 제작 수 있었다.